In Sunday's 6-3 loss to the Kansas City Royals, Castro dove for a ground ball off the bat of Alex Gordon and failed to get up and chase the ball after it deflected off his glove. Outfielder Reed Johnson ran in from center field to pick it up, and two runs scored in a four-run first inning.
The play resulted in a lecture but no benching from manager Mike Quade.
"I dived for the ball, and I thought the ball went [further in] in the outfield," the 21-year-old Castro said Monday. "The grass made it stop, and I thought the outfielder was going to get it. I looked bad on that play. That's not going to happen again. Normally I get up and chase that ball."
Quade sat Castro in September after Castro made a mental mistake by forgetting how many outs there were and didn't complete a double play, allowing an inning to continue.
Quade was asked why he chose not to bench Castro this time.
"Because he has been so good," Quade said. "I'm not in the habit of benching guys who make mistakes. Guys do that. I thought last year I saw more mental lapses from him."
Castro is in the midst of a 10-game hitting streak and is being touted as possibly the Cubs' lone All-Star representative. He is batting .326 and is third in baseball with 104 hits.
Bruce Levine covers the Cubs for ESPNChicago.com and ESPN 1000.